I would suggest adding s cylume lightstick for each child. They are nice comfort item for small child on a dark night and have some value as a signaling device. Plus they're fun and cheap.

Another option is to change from a waistpack to a brightly colored vest with everything in the pockets. The kids will be more visible and you'll know that they have their gear. The one problem with that is that I don't know of any commercial source for one. Maybe a child size hunting or fishing vest would work.